WeakSet.prototype.has()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

The has() method of WeakSet instances returns a boolean indicating whether an object exists in this WeakSet or not.

Try it

Syntax

has(value)

Parameters

value: The value to test for presence in the WeakSet.

Return value

Returns true if an element with the specified value exists in the WeakSet object; otherwise false. Always returns false if value is not an object or a non-registered symbol.

Examples

Using the `has()` method

const ws = new WeakSet();
const obj = {};
ws.add(window);

ws.has(window); // returns true
ws.has(obj); // returns false

// Storing a non-registered symbol
const sym = Symbol("foo");
ws.add(sym);
ws.add(Symbol.iterator);

Specifications

Specification
ECMAScript Language Specification # sec-weakset.prototype.has

Browser compatibility

	Desktop					Mobile						Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	Deno	Node.js
`has`	36	12	34	23	9	36	34	24	9	3.0	37	1.0	0.12.0